How Does London’s Underground Pollution Compare to Its Traffic?

Unfortunately for residents of the British capital, the words “pollution” and “London” are becoming almost synonymous. Despite attempts to reduce its effects by London mayor Sadiq Khan, the city is consistently exceeding EU standards and people living there are increasingly at risk of developing health problems.

But it isn’t just those living there. Commuters are also at risk of inhaling dangerous chemicals like nitrogen dioxide as well as particulate matter. London’s traffic is one of the main problems, but might the underground actually be worse?

Comparing the two

With diesel engines contributing a sizeable proportion of the city’s nitrogen dioxide levels, there are potential risks for cyclists as well as drivers who are both exposed to the dirty air for long periods. However, recent research suggests the tube is actually far worse.

A study by the University of Surrey found that levels of air pollution encountered by tube commuters was over eight times as bad as that of drivers in the city. By fitting commuters with monitors, researchers were able to track how much particulate matter they were exposed to on a daily commute.

Specifically, the tests were monitoring PM10, which are particles of between 2.6 and 10 micrometres. Car drivers were found to encounter levels of 8.2mg, while those on the tube were exposed to a massive 68mg. To put this into context, the World Health Organization recommends mean exposure of no more than 25mg over the course of 24 hours.

Other findings

The main reason for the difference is that drivers can close their windows and their car will filter out pollutants coming in through the air-con system. In the same sense, tube commuters suffer less with the windows closed, but the constant opening of doors will let a higher degree of particulate matter in.

As well as the main findings, Surrey researchers found that bus commuters were exposed to 38mg of PM10 on average. They also found that the afternoon and evening commute is less polluted than the morning journey. Ironically, their findings also confirm that while car drivers are exposed the least, they contribute the most pollutants to the surrounding environment.

The root of the cause

As well as cars, there is an ongoing battle with industrial emissions. They make up a significant proportion of carbon dioxide, nitrogen dioxide and particulate matter emissions. To tackle the problem, the EU has brought in new directives like the Industrial Emissions Directive. As discussed in ‘One Directive to Rule Them All’, the directive was implemented in British law in 2013. Since then, companies have had to adjust the way they work to adapt to the new regulatory regime.